GERM CELLS OF HERMAPHRODITES 205 
The investigators whose results have been de- 
scribed above have thus furnished three theories re- 
garding the differentiation of male and female germ 
cells in hermaphrodites: (1) In Sagitta, according 
to Elpatiewsky, it is an unequal distribution of the 
‘“besondere Kérper,”’ (2) in Helix, according to Ancel 
and Buresch, it is due to the presence or absence of a 
nurse cell in the immediate neighborhood, and (3) in 
Helix, Demoll considers it a result of the influence of 
the accessory chromosome. It is perfectly obvious 
that hermaphrodites offer exceptionally fine material 
for the study of the differentiation of germ cells, but 
that thus far the results have not furnished an ade- 
quate explanation of the phenomenon. The investi- 
gations of Boveri (1911), Schleip (1911), and Krueger 
(1912) on the chromosomes in hermaphroditic nema- 
todes may be discussed more profitably during the 
consideration of the chromosome cycle in the next 
chapter. 
Certain morphological and experimental studies 
on the germ glands of amphibians are of interest be- 
cause both oédgonia and spermatogonia are sometimes 
more or less closely associated in a single individual 
during the developmental stages, and may persist 
even in the adult germ glands of a number of species 
which are commonly considered dicecious. Pfliiger, 
for example, was able to separate the young of the 
frog, Rana temporaria, into three groups, males, fe- 
males, and hermaphrodites; the hermaphrodites 
developed into either males or females. Similar 
results were obtained by Schmidt-Marcel (1908) 
